Boston Computer Society - Sinclair Timex User Group Newsletter

GOGO The Buston Computer Society

SINCLAIR/TIMEX USER GROUP NEWSLETTER

Volume 1, Issue 6 December 1982

This newsletter is produced to inform group members of the agenda and
logistics for future meetings, as well as to recap and amplify the information
provided at the last meeting. It also provides a forum for members and
interested parties to communicate what they have learned or developed relating
to Sinclair and Timex computer products. Meetings are open to the public;
however, attendees are encouraged to join the Boston Computer Society (BCS).

NEXT USER GROUP MEETING

Date: Wednesday, December 15, 1982
Time: 7:00 p.m.
Place: Large Science Auditorium

UMass, Harbor Campus
(Directions on last page)

ACTIVITIES FOR THE NEXT MEETING

As promised, Mindware will provide the group with an update of their
product line. Specifically, they will describe the "QUICKLOADING" algorithn
that you may have read about in the advertisements.

One of the members has also volunteered to demonstrate the Sinclair
printer he ordered from Gladstone, if he receives it in time.

As in past meetings, we plan to break up into groups to discuss topics of
special interest following the formal presentations. Tentatively, we will
break into an advanced group and a beginner's group.

PLANS FOR FUTURE MEETINGS

The date for the meeting in January has been changed to the 12th of
January, the second (net third) Wednesday of the month. Sue Mahoney: will
report on the Consumer Electronics Show (CES) being held in Las Vegas, Nevada
ending that week. Of direct interest to us, Timex, and several Sinclair—Timex
related companies, will be there. This is the show where new products are
normally introduced,

ANNOUNCEMENT

Sue Mahoney has accepted the position of Technical Support Manager with
the Timex Computer Corporation in Waterbury, Connecticut. In this position,
she will be supporting sales, marketing, and the internal product development
groups. In addition, she will be supporting local user groups and consumers
through projects such as the 800-24-TIMEX hotline and the Timex Computer Club.
She plane to relocate to Connecticut, but will stay active in the local BCS
user group.

HELP! SEND IN YOUR SUGGESTIONS FOR ESTABLISHING OUR SOFTWARE LIBRARY.

HIGHLIGHTS FROM THE NOVEMBER MEETING

Last month’s meeting was well attended. Surprisingly, most attendees
were new members. This bodes well for the BCS, which is already the largest
independent personal computer society in the world.

Sue Mahoney introduced the BCS and the User Group, stressing again that
we need and depend on volunteer effort to keep going. Sue also gave a "plain
English" introduction of computer terminology, the Sinclair-Timex computer,
and peripherals. Particularly delectable was her description that “the
computer weighs 12 ounces, just like a soft-drink can, and the flat keyboard
can withstand peanut-butter sandwiches."

The main speaker last month was Bob Masters, who described the
- Sinekatr-Fimex ¥U-CALC-program (see his article-in this-issue). Bob used the
program at work to verify Blue Cross Claims forecasts. His illuminating talk
demonstrated why the spead-sheet program is so popular.

Also last month J. Michael Coughlin described a new product, the
non-volatile static memory kit from Hunter Products, 1630 Forest Hills Drive,
Okemos, ME 48864. At $32.00 postpaid, it is not less expensive than other
RAMs, but it has a special feature. Two transistors sense when power has been
disconnected and switch memory to a Lithium battery. The kit comes with 2 K
of RAM and sockets for up to 6 K more. The RAM chips it uses are the
HM 6116 LP-4, which have 2 K bytes and can be purchased for five to seven
dollars. Jumpers are provided to map the memory to any region. The kit is
not compatible with 64 K RAMs, since it only decodes 32 K. Delivery time was
two weeks.

George Peterson talked about a cart that he designed and built. He makes
it out of sturdy metal tubing and pieces of kitchen counter top -- the part
cut out for the sink! He claims that cart-building is just a hobby, but if
you make him an offer, who knows?

John Kemeny (no relation to Dr. J. G. Kemeny, co-inventor of BASIC) spoke
about the newsletter exchange program. In San Francisco, several user groups
“~~ —~have-joined-in-preducing a very delightful newsletter, SyncLink. Since the
last meeting, the ZX Users Group of New York has sent a newsletter; and the
Triangle Users’ Group in North Carolina is getting organized.

TO ERR IS HUMAN

A dead insect caused a program on an early vacuum tube computer to crash.
Since then flaws or errors in computers which cause results other than that
desired have been called "bugs." Hence, the term "debugging." it is safe to
say all large computer programs contain bugs. Bugs vary in severity from

minor annoyances to major flaws.

The ROM in the ZX-81 and TS-1000 contains a computer program. This
program decodes keyboard entries, checks the syntax of BASIC statements,
interprets statements when a program is run, and more. The 2X-81 ROM is
identical to that in the TS-1000. The ROM has been around for a couple of
years, so most of the bugs have been removed. Nonetheless, it contains bugs.
In the article below and in articles in future issues of the newsletter, we
will describe the bugs we’ve found. If you catch a bug, let us know.

BUG #1 (8 K ROM)

This bug will probably not sting you unless you are trying to interface
circuits of your own design with the computer, and only then if you cause
something to happen when you read from a particular address,

The bug occurs in ROM in the main display routine (which creates the TV
picture). A variable called FRAMES is decremented 60 times a second whenever
there is a display, In addition, code at 0229 hex loads FRAMES into the HL
register; and code at 0237 hex loads the B register from the address contained
in HL. The net effect is that the contents of each memory location is
sequentially loaded into the B register. (All memory may be read, but I only
verified that this occurs on the top 32 K.)

Why is this a bug? Remember our definition of a bug -- any program
characteristic that caused a result other than that desired. Your editor
designed a circuit which caused an external event whenever a particular
address was. read. (What-I- was-trying to do is not revelent to the current
discussion; perhaps it can be the subject of a future article.) I had planned
to use PEEK( X ), where X was greater than 32,768, to cause the external
circuit to perform its function. Since the computer reads from all memory
locations, the circuit was activated erroneously about every 9 minutes.

We are calling this a bug because there is no reason we could find for
the computer to be reading memory. If the instructions were selected for some
critical timing purpose, other instructions, which don’t read all of memory,
could have been used. It has also been conjectured that this code was
inserted to help debug the hardware and was never removed.

THE ANSWER TO LIFE, THE UNIVERSE, AND EVERYTHING (8 K ROM)

Many people think computers are a black boxes with answers in them, and
that programming is a way of extracting answers from the computer. On the TV
series, Hitchhiker’s Guide to the Galaxy (a BBC production broadcast on PBS),
the second greatest computer of all time answers "the" question. It took
7 1/2 million years to run the program to completion.

Fortunately, we had a monkey typing at random on our computer, and it
came up with a program which answers "the" question in only a few minutes. I
was frankly disappointed with the resuit. But, anyway, here is the program:

1 LET A$="I-SQR IDEXP(-PI*I)/PI**2"
10 PRINT "ENTER YOUR AGE™_
20 INPUT I

40 PRINT ,,,,"THE ANSWER TO LIFE,
THE UNIVERSE, AND EVERYTHING IS ";
42 LET I=vAL A$ (3 TO 4)
50 IF VAL A$ THEN GOTO 42
60 PRINT (STRS§ (VAL AS (6 TO 12))(3 TO 4)
70 PRINT "ENTER A FRIENDS AGE”
80 GOTO 20

The answer is, of course, a number. In case you do not believe that
there is a number which answers the mysteries of the Universe, I refer you to
Martin Gardner’s column in the November 1979 issue of Scientific American.

VU~CALC by Robert Masters

VU-CALC is Sinclair’s spread-sheet program. It essentially replaces the
accountant’s analysis sheets. It is a table made up of boxes. Each box can
contain a number, a label or title, or the result of a formula that is
attached to the box. Each box has up to 8 characters of information.

The VU-CALC table is 36 columns across and 26 rows down, giving 936
boxes. Displayed on the screen is a window of 3 columns by 9 rows. It is
easy to move around and change the location of the window by using the four
arrow keys (unshifted 5-8).

Forty formulae are allowed on the table. This. sounds like a limited
number until you understand the powerful use of formulae in VU-CALC. It took
me several hours. A formula can be set in many boxes. A “relative” formula
will act as a template and change the boxes it references as the formula is
moved around. A single instruction will assign a formula to an entire row or
column of boxes.

A formula can be up to 32 characters long. It can be constructed with
numbers, box references, parentheses, and the four operations: +, -, *, and /.

After data, titles, and formulae have been assigned, a calculate
instruction is entered. This evaluates all formulae and places the results
into the boxes where the formulae are attached. The calculation time will
vary from a few seconds to about a minute -- depending on the number and
complexity of formulae. The calculation in VU-CALC is done sequentially by
row, making it critical that a formula only references boxes above and to the
left of the box it is attached to.

VU-CALC Strengths

1. Economical. $14.95 + postage from Sinclair, $19.95 from the local Timex
retailer.

2. Reliable. Program loaded on first effort and has run reliably. I found

no bugs in the program (it’s mostly machine language). After a couple of

months, my copy of Sinclair VU-CALC had the tape bind in the cassette. it did
--—----_not—load_after_that, but I had made other copies.

3. Easy to Use. Most instructions are single keystrokes that work logically
and quickly. It tock me a while to get used to the instructions. There is
good error trapping. TI have never had to unplug and load again.

4, Fast. The instructions, including calculate, work quickly. The
performance is surprising. Entering your data and titles can take quite a
while, but that is a function of the amount of information entered.

5. Good Utility. The program can be put to practical use.

6. Powerful. VU-CALC is suprisingly powerful, especially in its use of
relative formulae.

VU-CALC Weaknesses

1. Small Window. I would like to be able to see more of the table at one
time. The window is limited by the screen size.

2. Table Flexibility. Once data is set, it cannot be easily moved around the
table. For example, data in rows or columns cannot be exchanged.

3. Titles. The window can not be made to keep titles over rows and columns.
It was sometimes difficult to remember my position on the screen. Row and
column numbers are maintained on the screen as location indicators.

4. Left Justification. I am used to seeing numbers with right justification
or centered around a decimal point.

VU-CALC Example

The figures below show two screens from a budget. The cursor is in box
AO] in Figure 1 and box DO4 in Figure 2. The "L" command loads numeric data
or labels. Note the eight place accuracy (longer strings are truncated).
Also note no dollar signs were used in the data. The formula attached to box
DO4 is displayed at the bottom of Figure 2. This formula was declared
"relative" and attached (in one operation) to all the boxes in the fourth
column between rows D and I. After entering the values for columns 2 and 3,
the CALCULATE command computes the balances.

Figure 1 Figure 2

VU-CALC Summary

VU-CALC is an excellent purchase that I recommend, Three actions should
be taken to minimize the weaknesses and maximize the performance you get:

1. Carefully draw out and plan the table before entering data and formulae.

I developed a planning sheet which greatly aided data and formula entry by
acting like a map.

2. Regularly repeat title boxes in order to have a reference that is always
on the screen.

3. Work at fully understanding how formulae are used before developing the
first serlous application.

Special Report by Robert H. Cushman
With Thanks to David Grundy, Ferranti Electric (U.K.)
Reprinted from EDN, November 1982
© CAHNERS Publishing Co.

Gate arrays eliminate TTL glue in a high-volume product

In some designs, a gate array can
efficiently and economically re-
place assorted SSI and MSI TTL.
In the Sinclair personal computer,
for example, designers had to
combine 17 TTL parts in one
Package to achieve a retail price
of less than $100. Use of a gate

The functions to be integrated
were unusually diverse, including
an oscillator for the computer's
280 LP, a video interface (US and
European TV standards), two cas-
sette interfaces and memory-
control circuitry. The designers

used a Ferranti bipolar gate array,
partially because the Ferranti
Process accommodates some lin-
ear Circuits and partially because
it's sufficiently simple to reliably
turn out millions of units per year
(it requires only six steps).
According to Ferranti, this appli-
Cation represents a design situa-
tion where a gate array is as
economical as a full-custom solu-
tion, even if volume rises into the
tens of millions of units. The
reason? A large number of func-
tions are being integrated, and
each requires its own I/O. The

final chip size (130 mils square)
was determined by the number of
required pads, and even though
using a fully custom design would
have produced a 30 to 40%
smaller active area than that of the
gate array, the chip size would
have remained the same.

Although Sinclair won't release
actual cost figures, EDN specu-
lates that the gate array costs
$0.01 per gate. For 500 gates, this
comes to $5. At the millions-of-
units-per-year sales level, this
price should drop below $5.

REGULATOR,

GATE ARRAY

(a). The redesigned unit (b) uses only four ICs: the Z80, the 24-pin ROM (in a
@ 4718 byte-wide RAM and a Ferranti ULA 810 2 gate-array IC.

101

ROM TEST

Often I marvel at the amount of information stored in my computer -- both
in RAM, a user changeable random-access memory, and in ROM, a fixed, read-only
memory which makes user programs work. In the ROM, 8 K bytes of program and
data are stored. This is 8 x 1024 = 8192 bytes or 65,536 bits of information.
Each bit is either a 1 or 0 depending on what the designer wanted to do.

If one of those 64 K bits were in error, would the computer operate
properly? It is conceivable that the error would be such that it would never
be noticed. However, it could cause the computer to bomb. ROM errors don’t
occur frequently, but I felt I needed a means of reassuring myself that my ROM
did not contain an error. Thus, I devised a ROM checksum. This error
checking technique is similar to "Syncsum" in Sync or "Syntactic Sum" in
Syntax (which are used to verify correct program entry). The program is
capable of running on any Sinclair or Timex computer.

5 LET K=8
seas HG, 10. LET A=0
20 LET B=0

30 FOR I=1 TO 1024*K

50 LET A=A+PEEK(I-1)

60 IF A<1000 THEN GOTO 90
70 LET B=Bt1

80 LET A=A~1000

90 NEXT I

100 PRINT B;A

Using this program, which takes a few minutes to run in FAST mode, I got
the checksum, 855106. So did several of my friends. This indicates that we
probably all have the same ROM (the test is not foolproof). If you have the
old 6 K ROM (the one with known bugs in it), let us know what sum you get.
This technique could be used to identify ROMs. Changing line 5 to LET K=4,
the sum is 428876. With a 4 K ROM (ZX-80) and K=4, the sum is 390829.

G#L*S "SZ"!

If you publish programs, you will publish bugs. Well, there is one in
the Tholean Web program from our last newsletter. In the second program,
“three-dimensional looking...," you need to change line 50 to

50 LET X1=21 - LEN PS

Without the change, the program tries to write below line 20 and terminates
with error 5. Also, we should have suggested that lines 115 and 135 on the
bottom of the page be added to the original program. It is easier to observe
the "bouncing" ball with the simplier pattern.

Finally, we forgot about people with 1 K RAM (sorry). Since a full
display takes 768 bytes, it is nearly impossible to run any program in al K
system which uses the entire screen. Delete all REM statements and modify
lines 50 and 60 as follows:

50 LET X1=10-LEN PS
60 LET Y1=12

HINT: When memory is nearly full, a line that you EDIT will not be displayed
(it is there, but the TV picture is cropped). To see what you are doing:
LIST the line, then immediately EDIT.

ANY REVIEWERS OUT THERE?

There are many books coming out on the Sinclair-Timex computer. Wiley
Publishing just introduced Byting Deeper into Your TS-1000/ZX=81 for $12.50.
In addition, Thomas A. Bell, editor of the General Books Division of
Addison-Wesley Publishing, said they are co~publishing, with the New American
Library, an entire series of paperbacks in the $3.50 to $7.00 range.

FOR MORE INFORMATION

Sue Mahoney, Director of the Sinclair/Timex User Group
c/o The Boston Computer Society or call (203) 573-5816.

Cliff Danielson, Newsletter Editor
14 Davis Road, Chelmsford, MA 01824, (617) 256-4638.

John Kemeny, Contributing Editor & Correspondent With Other User Groups
284 Great Road, Apt. D5, Acton, MA 01720.

DIRECTLONS TO THE MEETING

The Sinclair/Timex User Group meets in the Large Science Auditorium (Room
8/2/009) of the University of Massachussets of Boston, Harbor Campus. The
Harbor Campus is only three miles from downtown Boston and easily accessible
by public and private transportation. From the north or west, take the
Southeast Expressway to Exit 17. Turn left onto Columbia Road. Enter the
rotary and take the first right (Morrissey Boulevard). Bear right on the
traffic island, following UMass/Boston sign. Turn left into the Campus. From
the south, take Morrissey Boulevard northward to the campus. On the MBTA,
take the Red Line (Ashmont Train) to Columbia Station. Transfer to the free
University shuttlebus in the T parking lot.

IMPORTANT NOTICE ! 1! If the mailing label on this newsletter is
handwritten, then you are not on the mailing list of the Sinclair-Timex User
Group. You need to either join the BCS or, if you are a BCS member, contact
Mary McCann in the BCS office to be added to the Sinclair-Timex mailing list.

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